Index: head/Makefile.inc1
===================================================================
--- head/Makefile.inc1
+++ head/Makefile.inc1
@@ -1140,6 +1140,8 @@
 .if empty(INSTALLKERNEL) && !defined(NO_INSTALLKERNEL)
 INSTALLKERNEL= ${_kernel}
 .endif
+.else
+.error Missing KERNCONF ${KERNCONFDIR}/${_kernel}
 .endif
 .endfor